title: Augmentation of spontaneous macrophage-mediated cytolysis by eosinophil peroxidase.
abstract: Eosinophil peroxidase (EPO), a cationic protein purified from horse blood, adhered to four different types of tumor cells, markedly potentiating their lysis by preformed or enzymatically generated H(2)0(2) (up to 76-fold, as assayed in serum-containing tissue culture medium without supplemental halide). Similarly, compared with uncoated tumor cells, EPO-coated tumor cells were up to 32 times more sensitive to lysis when incubated with macrophages or granulocytes whose respiratory burst was triggered by PMA. However, EPO-coated tumor cells were also readily lysed by bacillus Calmette- Guerin-activated macrophages in the absence of exogenous triggering agents. This spontaneous cytolysis was rapid (50 percent at 2 h) and potent (50 percent lysis at macrophage/tumor cell ratios of 1.5 to 4.6), and was observed with both a peroxide-sensitive tumor (TLX9) and a peroxide-resistant tumor (NK lymphoma). Under the conditions used, neither EPO alone nor macrophages alone were spontaneously cytolytic. Neither EPO nor EPO-coated tumor cells triggered a detectable increment in H(2)0(2) release from macrophages. Nonetheless, spontaneous macrophage-mediated cytolysis of EPO- coated tumor cells was completely inhibitable by catalase (50 percent inhibition, 23 U/ml), although not by heated catalase, indicating a requirement for H(2)0(2). Cytolysis was also completely inhibitable by azide (50 percent inhibition, 2.6 X 10 -5 M), indicating a requirement for enzymatic activity of EPO. Thus, a cytophilic peroxidase from eosinophils and H(2)0(2) spontaneously released from activated macrophages interacted synergistically in a physiologic medium to destroy tumor cells.
mesh_terms: D000818:Animals; D001965:Bromides / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D047209:Eosinophil Peroxidase; D004804:Eosinophils / Q000201:enzymology*; D005260:Female; D006736:Horses; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007454:Iodides / Q000494:pharmacology; D008223:Lymphoma / Q000276:immunology; D008262:Macrophage Activation; D008264:Macrophages / Q000378:metabolism*; D012515:Mast-Cell Sarcoma / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D010544:Peroxidases / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
chemical_list: D001965:Bromides; D002712:Chlorides; D007454:Iodides; D006861:Hydrogen Peroxide; D047209:Eosinophil Peroxidase; D010544:Peroxidases; D013755:Tetradecanoylphorbol Acetate